Matrix-assisted laser desorption/ionization and electrospray ionization mass spectrometry: sodium-cationized oligosaccharides do not exhibit "internal-residue loss" rearrangement

A series of methylgalactotrioses, in which one or two residues were specifi cally deoxygenated and labeled with a fluorine atom in the C-3 position, we re used as models for the study of "internal residue loss" (IRL) under the conditions of matrix-assisted laser desorption/ionization time-of-flight (M ALDI-TOF) and electrospray ionization (ESI) techniques. Under the condition s of measurement of MALDI-TOF post-source decay and ESI in-source decay of methyl oligosaccharides, the IRL rearrangement of [M + Na](+) ions did not take place.